This invention relates to tufting machines and more particularly to apparatus for preventing the needles from sewing through or tagging the previously formed loops as the needles reciprocate downwardly through the base fabric to form the successive loop.
Sew-thru is the situation in which the needle, as it descends to form a loop, enters a previously formed loop and in effect forms a chain stitch. A similar situation known as tagging occurs where the needle, rather than passing clearly through the previous loop spears some of the filaments. Both situations tend to occur in tufting machines producing loop pile under circumstances where either the twist of the yarn is such that the loop, upon being shed by the looper, curls or springs back under the path of the needle; the stitches formed per inch of base material is large such that the loops have not moved very far in the feed direction when the needle next penetrates the base fabric; or the pile height of the loops formed is relatively large and are not pulled back very far toward the base fabric thereby swinging into the needle path.
The accompanying sew-thru and tagging is not a problem in cut pile tufting machines because the previously formed loop remains on the looper, being prevented from entering the needle path by the barb on the tip of the cut pile looper. Moreover, even if the needle should spear such a previously formed loop the fact that the loops are later cut on the looper eliminates the visible aesthetic defects which clearly show on uncut loop pile.
Heretofore, although these problems exist they have not been of major significance in cut/loop tufting machines, i.e., those where loop pile and cut pile selectively are produced in the same row of stitching since the uncut loops of pile have been back-drawn from the seizing position toward the base fabric. Those machines, as illustrated in U.S. Pat. No. 3,084,645, back-draws the uncut loops past a spring clip on the looper while the cut loops, which are not back-drawn, remain on the looper and are cut. Thus, the uncut loops are shorter than the cut pile and generally the machine can be timed so that most loops do not significantly swing into the needle path. However, in the recent even level cut/loop pile machines, such as illustrated in U.S. Pat. No. 4,134,347, the loops which are prevented by the gate from entering the loopers are merely released and only drawn-back to substantially the level of the looper blade so that the uncut loops are substantially at the same level as the uncut pile. The pile height of tufted fabric produced with this construction is in the order of 3/4 inch, relatively high pile resulting in more than an occasional sew-thru condition. The problem, of course becomes more acute as the pile height is increased. Moreover, this difficulty is exceptionally significant when the gauge of these machines has been decreased to one eighth.
The known prior art efforts to reduce tagging, are illustrated in U.S. Pat. Nos. 2,975,736; 3,074,362; and 3,316,867. In U.S. Pat. No. 2,975,736 a needle guide channel plate was proposed for a loop pile machine in an earlier stage in the development of the tufting art when the gauge was substantially larger than the gauge at the present stage and more space was available beneath the bedplate. In U.S. Pat. No. 3,074,362, a bristle brush fixedly mounted to the bedplate of a loop pile machine held the formed loops from curling back into the needle path. Being fixed, its applicability to a machine forming both cut and uncut pile presents difficulties and was unsuccessful when installed in a one eighth gauge level cut/loop machine. In U.S. Pat. No. 3,316,867 the head of the machine is inclined to alter the path of the needle and thus was not found to be a practical solution.